1. Field of Invention
.alpha.-Galactosidase (E.C 1.2.1.22) is an enzyme able to hydrolyse melibiose to galactose and glucose. Some yeast species (Saccharomyces cerevisiae var. oleaceus, Saccharomyces cerevisiae var. oleaginosus, S. cerevisiae var. uvarum and Saccharomyces cerevisiae var. carlbergensis) are able to produce this enzyme naturally, but industrially used baker's and distiller's yeast strains (which belong to S. cerevisiae) do not produce this enzyme. This results in incomplete use of raffinose of molasses, which is widely used as a substrate for the production of baker's and distiller's yeast and sometimes used for alcohol production.
This invention comprises the construction of new baker's and distiller's yeast strains, which produce .alpha.-galactosidase. This invention comprises also the construction of new brewer's yeast strains able to produce .alpha.-galactosidase, which gives an improved method to monitor the pasteurization of beer. Inserting an .alpha.-galactosidase gene in one's baker's, distiller's or brewer's yeast provides a method of marking one's own strains or e.g. the beer produced.
2. Brief Description of the Background